1498-89-1Relevant articles and documents
Investigating the Photochemistry of Spiropyran Metal Complexes with Online LED-NMR
Feuerstein, Thomas J.,Müller, Rouven,Barner-Kowollik, Christopher,Roesky, Peter W.
, p. 15479 - 15486 (2019)
As one of the best studied photoswitches, spiropyrans (SPs) have attracted significant interest in the scientific community. Among the many stimuli to alter the isomerization into the merocyanine (MC) isomer, such as temperature, pH, solvent polarity, redox potential, or mechanical force, the ability of the MC form to act as a ligand site for metal complexation has recently raised new attention. We herein synthesize hitherto undescribed coordination compounds of 8-methoxy-1′,3′,3′-trimethyl-6-nitrospiro-[chromene-2,2′-indoline] with s-block ([Ca(MC)4](ClO4)2), d-block ([Zn(MC)2(MeCN)2](ClO4)2, [Ni(MC)2(MeCN)2](ClO4)2), as well as f-block ([La(NO3)3(MC)2]) metals. All complexes are structurally described by X-ray crystallography and systematically investigated in solution via Job's method of continuous variations (Job plots), as well as online NMR spectroscopic kinetic experiments with in situ irradiation of the analyte solution inside the NMR spectrometer (LED-NMR). We can unambiguously identify the photoresponsive nature of the complexes in solution, which is a crucial step toward the application of these promising molecules in material science.
Kinetic Analysis of Photochromic Systems under Continuous Irradiation. Application to Spiropyrans
Pimienta, V.,Lavabre, D.,Levy, G.,Samat, A.,Guglielmetti, R.,Micheau, J. C.
, p. 4485 - 4490 (1996)
The kinetics of spiropyran photochromic systems in solution in a stirred batch reactor continuously irradiated with monochromatic light was studied by UV/visible spectrophotometry.The plots of absorbance vs time were analyzed, and the desired parameters (quantum yields, UV/visible spectrum of the unstable photomerocyanine, ...) were extracted from an iterative computation which fitted the calculated curves to the experimental ones on the basis of a representative model of the reaction mechanism.The method was applied to spiro whose corresponding photomerocyanine has a lifetime of 100 s in toluene; the two quantum yields of the direct process of photocoloration and the reverse reaction of photobleaching could be determined along with the spectrum of the corresponding photomerocyanine.To demonstrate the general nature of the photokinetic method, it was applied to the reaction of spiro, where the main photochromic process is accompanied by a photodegradation.Despite this interfering phenomenon, the photokinetic method could be used to extract the parameters of the main photochromic process.It also showed that the photodegradation products catalyzed the termal back-isomerization.The order of magnitude of the rate constant of this catalytic process and the quantum yields of photodegradation were estimated.
Decoloration rates of a photomerocyanine dye as a visual probe into hydrogen bonding interactions
Ciampi, Simone,Eggers, Paul K.,Haworth, Naomi L.,Darwish, Nadim,Wagner, Pawel,Coote, Michelle L.,Wallace, Gordon G.,Raston, Colin L.
supporting information, p. 4815 - 4818 (2015/03/18)
We have developed a visual marker for the investigation of hydrogen bonding (HB) effects. The decoloration rate of a photochromic dye that incorporates a latent intra-molecular HB feature can be linked to the HB character of the media. Kinetic and thermodynamic parameters of this simple decoloration approach for HB sensing are investigated both experimentally and by high level theoretical studies. This principle has been applied for the detection of changes in the HB character of stationary and fluidic systems. A major finding is the observation of a shear-related perturbation of the balance between intra- and inter-molecular HB within a dynamic thin film.
Photochromism of nitrospiropyrans: Effects of structure, solvent and temperature
Goerner
, p. 416 - 423 (2007/10/03)
The thermal and photochemical ring opening and ring closure of the spiropyran/merocyanine couple of three nitro-substituted spiropyrans (6-NO2: 6, 7 and 8-NO2: 8) were studied and the results were compared with those of other 6-NO2 spirobenzopyranindolines (BIPS) (1-5). The photocolouration, which occurs in the triplet manifold throughout, and the photochemical conversion and thermal relaxation of the two observable photomerocyanines into the closed spiropyran (Sp) form (decolouration) were quantified as a function of solvent polarity and temperature. The relaxation time (τt-Sp) at 25°C ranges from 2 s for 5 in methylcyclohexane to 104 s for 7 in ethanol. This large variation in τt-Sp is due to changes in both the activation energy (Ea = 75-105 kJ mol-1, increasing with polarity) and the pre-exponential factor (A = 1012-1015 s-1). The quantum yield of colouration with 308 nm pulses is substantial in solvents of low polarity (φcol = 0.3-0.8) and decreases (c→t = 30-40 kJ mol-1. The effects of substituents and medium properties are described and the mechanism of photochromism is discussed.
